Total sulfur analyzer and method

ABSTRACT

A TOTAL SULFUR ANALYZER AND METHOD WHEREIN A HYDROCARBON SAMPLE USUALLY IN LIQUID FORM AND HAVING SULFUR OR SULFUR COMPOUNDS THEREWITH, IS PYROLYZED TO CONVERT THE HYDROCARBONS TO LIGHTER MOLECULAR WEIGHT HYDROCARBONS, SUCH AS METHANE, WHICH IS GASEOUS AT AMBIENT TEMPERATURES, AND THEN THE GASEOUS SAMPLE IS HYDROGENATED TO CON-   VERT THE SULFUR IN THE SAMPLE INTO HYDROGEN SULFIDE WHICH IS THEN MEASURED BY A HYDROGEN SULFIDE MEASURING DEVICE, WHEREBY THE TOTAL SULFUR CONTENT OF THE SAMPLE, REGARDLESS OF ITS ORGINIAL FORM IN THE SAMPLE, IS ANALYZED.

P 4, 1973 c. KIMBELL 3,756,781

TOTAL SULFUR ANALYZER AND METHOD Filed May' 18, 1971 2 Sheets-Sheet 1 [NI EN TOR Czar/e: 1. M27748 lume! Willow & MaflLewA ATTORNEYS 3,756,781 TOTAL SULFUR ANALYZER AND METHOD Charles L. Kimball, 9441 Baythorne, Houston, Tex. Filed May 18, 1971, Ser. No. 144,434 Int. Cl. G01n 31/12 US. Cl. 23-230 PC 12 Claims ABSTRACT OF THE DISCLOSURE A total sulfur analyzer and method wherein a hydrocarbon sample usually in liquid form and having sulfur or sulfur compounds therewith, is pyrolyzed to convert the hydrocarbons to lighter molecular weight hydrocarbons, such as methane, which is gaseous at ambient temperatures, and then the gaseous sample is hydrogenated to convert the sulfur in the sample into hydrogen sulfide which is then measured by a hydrogen sulfide measuring device, whereby the total sulfur content of the sample, regardless of its original form in the sample, is analyzed.

BACKGROUND OF THE INVENTION The field of this invention is apparatus for measuring the quantity of sulfur present in hydrocarbon samples.

In chemical processes employing catalysts, the presence of even minute quantities of sulfur will radically effect catalytic action. Commercial practices frequently require the removal of sulfur contained in hydrocarbons. Therefore, it has been highly desirable for a number of years to have apparatus which could determine the quantity of sulfur in the original processing materials as well as in the output or product after sulfur removal treatment to verify the effectiveness of the removal.

Various techniques and procedures for measuring the total sulfur present in hydrocarbons and the like have been used and attempted in the past, each of which has its shortcomings. For example, X-ray fluorescence, titration methods, and wickbold oxyhydrogen burners have been used. Hydrogenation methods have also been employed for converting the sulfur content into hydrogen sulfide, but so far as known, these prior processes have not been satisfactory because of the deposition of carbon in and near the heated zone and because liquids are vaporized and condense out in cool zones of the equipment, thus producing unwanted deposits. In addition, so far as known, no prior apparatus has had the ability to provide a continuous reading of the sulfur content in a continuously fed sample stream.

SUMMARY OF THE INVENTION The present invention relates to a total sulfur analyzer in which means are provided for converting a hydrocarbon sample into a light hydrocarbon or hydrocarbons which is gaseous at ambient temperatures so that the entire apparatus does not have to be heated to high temperatures to maintain the sample gaseous and deposition of solid or liquid hydrocarbons in the apparatus is avoided. The gaseous hydrocarbon with the sulfur or sulfur compounds therewith is thus hydrogenated to produce hydrogen sulfide which is measured. The hydrocarbon or other material containing the sulfur or sulfur compounds is sampled on a continuing basis so that a substantially continuous readout of the sulfur content of the sample is obtained.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevation of the sulfur analyzer of this invention;

FIG. 2 is an enlarged view, partly in section, taken on line 2-2 of FIG. 1 and illustrating one form of a mechanism for moving a rotary sampler of the sulfur analyzer;

FIGS. 3 and 3A are sectional views illustrating two op- United States Patent O erative positions of the rotary sampler which is preferably utilized in the apparatus of FIG. 1; and

FIGS. 4 and 4A are sectional views which illustrate operational positions of a backflush valve which is preferably utilized in the apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, the letter A designates generally the total sulfur analyzer of this invention which is preferably mounted upon a panel or board B which is suitably affixed to a wall or other supporting surface (not shown). The principal components of the sulfur analyzer A are: a flow control unit or means F, a pyrolysis unit P, a hydrogenator H, an automatic catalyst reactivator R, and a hydrogen sulfide readout device C. Briefly, and as will be explained more in detail hereinafter, the apparatus and method of this invention involve the pyrolysis of a sample which may be a liquid, solid or a gas of relatively heavy hydrocarbons so as to convert any heavy hydrocarbons into light or low molecular weight hydrocarbons, usually methane, which is gaseous at ambient temperatures. The gaseous sample is then hydrogenated in the presence of a catalyst so that the sulfur which was originally present with the sample is then converted into hydrogen sulfide and the quantity thereof may then be measured, using a hydrogen sulfide analyzer C which may for example be of the type shown in US. Pat. No. 3,464,799.

Considering more specifically the details of the present invention, a typical commercial installation of the analyzer A of this invention is illustrated in FIG. 1 wherein all of the components are mounted upon the common panel or back B, with each of the principal components in the explosion proof boxes, as will be more fully explained. The analyzer apparatus A illustrated in FIG. 1 is particularly designed for a continuous flow stream of a liquid sample, usually a hydrocarbon sample having from five to twenty carbon atoms, examples of which are kerosene, naphthalene and gasoline. The liquid sample may have sulfur present as pure sulfur or in compound form, for example, as a mercaptan, sulfur dioxide, carbonyl sulfide or hydrogen sulfide. The present invention is adapted to measure the total sulfur present in such sample, regardless of the form in which the sulfur is present in the sample.

The liquid sample is introduced at an inlet pipe 10 through a valve 11. A conventional liquid flow meter 12 indicates the rate of flow of the stream of the liquid sample entering the analyzer A. Pressure gauges 14 and 15 are disposed in the line 10 preceding and following the flow meter 12, respectively. In this connection, a check valve 16 is provided in the flow pipe and it is set to open at a predetermined pressure so as to bypass any of the liquid sample for reducing the pressure thereof.

The main sample flow passes through a flow tube 17 to a backfiush valve 20. With the valve 20 in the normal operating position, the sample will flow from line 17 through the valve 20 and into flow pipe or line 21 which leads to the flow control unit F. The normal setting of the valve 20 is illustrated in particular in FIG. 4 and the purpose thereof will be more fully explained hereinafter.

The flow control unit F includes a rotary sampler 25 which is illustrated in two operative positions in FIGS. 3 and 3A. In the sample receiving position of the sampler 25, illustrated in FIG. 3, the internal rotating element 25a is shown with its sample receiving port 25b disposed in alignment with the fiow line 21 and a discharge line 22. It should be noted that the discharge line 22 is connected with the backflush valve 20 as illustrated in FIG. 4 during normal operations so that fiow of the sample therethrough to the bypass output 18 is permitted.

The rotatable element 25a of the rotary sampler 25 is disposed in a fixed housing 250, to which the lines 21 and 22 are connected as best seen in FIG. 3. Also, flow lines 23 and 24 are connected to such housing 250 and they are in communication with a sampler receiving slot 25d under normal operating conditions (FIG. 3). As will be explained more in detail hereinafter, hydrogen is introduced through the line 23 to sweep the sample in the slot 25d into the line 24 for flow to the pyrolysis unit P. The rotary member or element 25a also has sample receiving slots 25e and 25f which serve the same functions as heretofore described with respect to slots 25b and 25d when they are properly aligned with the flow tubes feeding the sample and the hydrogen as will be more evident hereinafter. For example, in FIG. 3A, the rotary member 25a is shown after a one-quarter revolution which positions the sample receiving slot 25b in position for the hydrogen gas flowing from the passage 23 through the slot 25b to the line 24 to sweep the sample to the pyrolysis unit P. At the same time, a new sample is received in the sample receiving slot 25 from the line 21.

Instead of having the rotary element or member 25a rotated in a single direction, it may be actuated in a reciprocating rotary motion, utilizing only the slots 25b and 25d. For example, as illustrated in the drawings and in particular to FIGS. 1 and 2, an air actuated piston 30 disposed in a cylinder 31 is connected to a linkage 32 which is in turn connected to a shaft 25g which is secured to the rotatable element 25a (FIG. 3). The shaft 25g is preferably supported in pillow block bearings 26 which are mounted on the panel B (FIG. 2) or are otherwise mounted within the explosion proof box for the flow control unit F. Air is admitted alternately into the cylinder 31 through flow lines 31a and 31b, preferably using solenoid controlled valves 33 and 34 which are regulated through a timer 35 of any conventional construction. As the piston 30 is reciprocated by the alternate introduction and release of air within the cylinder 31 through the lines 31a and 31b, the shaft 25g is turned so as to move the sample receiving passage 25b from the position shown in FIG. 3 to the position shown in FIG. 3A, and then upon the movement of the piston 30 in the reverse direction, the member 25 is reversed in its direction of rotation so as to return the slot 25b from the position shown in FIG. 3A to the position shown in FIG. 3. When such reciprocating operation is utilized, a sample is received only in the slot 25b, and the slot 25d is used only as a means to allow the passage of hydrogen to the pyrolysis unit P while a sample is being received in the slot 25b. The other slots 25e and 25 are not employed in such a system. It will be appreciated that other variations in the apparatus and manner of controlling the flow rate of the liquid sample or other sample may be utilized. The particular rotary sampler heretofore described is particularly advantageous with the present apparatus because it measures out a small known quantity of the sample and it controls the feed rate of such samples so that the amount of sulfur can be measured accurately with respect to the continuous feed of the sample, thereby providing an accurate measure of the quantity of the sulfur present in the sample, usually in a parts per million ratio of the sulfur to the sample. The sample slot 251; and each of the other sample slots, preferably receive and measure out a five microliter sample on each stroke. The five microliters of the sample are preferably controlled so that each of such samples is introduced with the flowing hydrogen stream into the pyrolysis unit P at one minute intervals which is set by the timer 35. It will be understood that such quantities and rate of flow are subject to variation by those skilled in the art.

The pyrolysis unit P is a conventional unit which includes a pyrolysis heating tube 35 having a heating element or elements wrapped around it and which is adapted to heat the sample flowing therethrough at a controlled velocity to a temperature of about 700 C. which effects a chemical breakdown of heavy molecular weight hydrocarbons such as kerosene into low molecular weight hydrocarbons such as methane which is gaseous at ambient or room temperatures. By way of example, the temperature in the pyrolysis unit 35 may be as high as 700 C. when the sample is kerosene being fed at the rate of five microliters per minute and with a flow of the hydrogen at a rate of approximately 0.8 cubic feet per hour. An excess of hydrogen is required in carrying out the method of this invention so that the carbon atoms which are produced by the fragmentation of the sample by the pyrolysis in the pyrolysis unit P can combine with the hydrogen to form the light hydrocarbon or hydrocarbons. Because the sample is converted to a gaseous material which is gaseous at ambient temperatures, this means that the rest of the apparatus A can be operated at ambient temperatures without a recondensation of the hydrocarbons in the flow system. This is important because if the entire analyzer apparatus A had to be maintained at a relatively high temperature to prevent condensation of the hydrocarbons, as is the case when only vaporization is utilized for rendering the sample gaseous, the various electrical components and other parts of the apparatus would malfunction or deteriorate so rapidly that they would become inoperable and unusable from a practical standpoint.

A visual indicator 36 is provided in the outlet line 35a from the pyrolysis unit 35, which has distilled water 36a therein through which the gaseous sample is passed and then is discharged through a flow line 37 having a pres sure gauge 77a therewith for flow to the hydrogenator H, as will be explained. The visual indicator 36 is provided so that any quantities of oil which are present in the gas will form a film or layer in the water 36a which will reveal the deficient operation of the pyrolysis unit 35 to the operator.

The line 37 has a pop-off valve 37a therein which is set to pop off at a predetermined back pressure, for example, 10 p.s.i. Except for such gas as may be discharged through the pop-off valve 37a, the sample gas with the hydrogen which was introduced through the line 23 passes through the line 37 into the hydrogenator H which is of conventional construction and includes a catalyst of platinum or other known material. The catalyst is contained within the tube or chamber 38 of the hydrogenator H so that the sample gas and the hydrogen flow across the catalyst and hydrogen sulfide is formed by the reaction of the hydrogen and the sulfur in the sample, regardless of the form in which the sulfur was originally present, so that such hydrogen sulfide is then released from the hydrogenator H and flows through a tube 39 to a flow meter 39a and then into the hydrogen sulfide analyzer or measuring apparatus C. The details of the hydrogen sulfide analyzer C are not disclosed herein because such analyzer is fully disclosed in U.S. Pat. No. 3,464,799. However, the general arrangement of the analyzer C in conjunction with the rest of the components with the apparatus A has been illustrated in FIG. 1.

In the preferred form of the invention the hydrogen which is used in the hydrogenator H is introduced as pure hydrogen at about 30 p.s.i. through an inlet tube or pipe 40 at a flow meter 40a. The hydrogen is bubbled through a humidifier bubbler 41 having distilled water therein to remove carbon therewith and then the hydrogen passes from bubbler 41 through a flow pipe 42 which fiows to a solenoid controlled valve 43 mounted in the catalyst reactivator unit R. The solenoid valve 43 is normally open so that the hydrogen flows from the line 42 into the line 23 and then through the valve 25 as previously explained. When it is desired to reactivate the platinum catalyst, or other catalyst in the hydrogenator chamber 38, which normally would occur every twelce hours of commercial operation, the reactivator R is utilized. First, a purging of the system is effected, utilizing nitrogen introduced through a flow line 50, which is provided with a safety pressure switch 51 so that if such nitrogen is not being properly supplied from the source through the line 50, the entire burn olf cycle of the reactivation procedure is cut of? electrically.

A solenoid actuated valve 44 is actuated by a suitable timer control 45 so as to simultaneously close the valve 43 with respect to the hydrogen flow from the line 42 and to open the valve 44 to flow nitrogen from the line 52 through the line 52a and then through the valve 43 to the line 23. With the rotary sampler 25 in the position shown in FIG. 3, the nitrogen then flushes through the pyrolysis unit P and through the hydrogenator H to completely sweep out any hydrogen from the system so that no explosion occurs when air is subsequently introduced. After three minutes of such purging, the timer 45 actuates the solenoid 44 to close off the flow of nitrogen from the line 52 and to admit air through line 53 at about 30 psi. Air then flows through the valves 44 and 43 and the line 23 into the pyrolysis unit P and into the hydrogenator H. The system is then filled with air so that any carbon deposits or other contaminats in the pyrolysis unit or in the hydrogenator are burned off. At the same time, the temperature in the pyrolysis unit P or in a burn-01f unit 35b is increased to about 900 C. to promote the burn off of any excess carbon which might have accumulated just following the pyrolysis unit P. Thereby, the catalyst is regenerated in the hydrogenator for subsequent use. After approximately five minutes of such regeneration by the burn off of the carbon in the pyrolysis unit and hydrogenator, the timer 45 acts to again return the valve 44 to cut off the flow of the air through the line 52 and to allow the flow of the nitrogen from the line 52 into the line 23 so as to purge all air from the system with the nitrogen. After approximately three minutes of such purging with the nitrogen, the valve 43 is switched to the normal hydrogen flow and then the system is ready for normal operation with the hydrogen being supplied through the line 23 to the flow control unit F.

In the event the apparatus A of this invention is mounted outside or in conditions wherein the temperature to which the apparatus A is exposed may vary over a wide range, it is usually desirable to provide a heater of any conventional construction such as indicated at K. The heater K is disposed within an outer housing confining the entire apparatus A so as to maintain a substantially constant temperature of the entire apparatus A. Normally the temperature is maintained in the neighborhood of 75 F. and a switch 60 is used for controlling the temperature. The heater is preferably an electrical heating unit which has electrical power supplied thereto through an electrical conduit 61 or by any other suitable means. A thermostat 62 is preferably incorporated with the heater K.

Electricity is supplied to the analyzer A of this invention in any manner, but as illustrated in the drawings, electrical pipe or conduit is shown connecting the various explosion proof boxes and through which the electrical wires are passed for making the electrical connections for the various electrical components of each of the units. The power supply is connected through an electrical conduit or pipe 65 in the preferred arrangement illustrated in FIG. 1, with a box being provided for electrical connection indicated at 66. An analyzer switch 67 and a catalyst switch 68 are provided in the system for ready accessibility in controlling the electricity to such components. The power to the measuring device or analyzer C is supplied through the pipe or conduit 70.

It should also be noted that nitrogen is supplied to each of the explosion proof units through a line 80 so as to prevent explosions which might otherwise occur if oxygen were present with the apparatus during the flow of the hydrogen therethrough.

Although the backflush 'valve 20 is normally in the position shown in FIG. 4, it is turned to the position shown in FIG. 4A to flush out the rotary sampler '25 periodically to prevent the accumulation of any deposits which might interfere with an accurate sampling. Thus, when the backflush valve 20 is turned to the backflush position of FIG. 4A, the incoming sample is directed in a reverse direction through the sampling slot 25b and then is discharged through outlet 18.

In the operation of the analyzer A of this invention, and in carrying out the method of this invention, the liquid sample is introduced through the line 10 and it flows then through the flow control unit F. The backflush valve 20 is in the position shown in FIG. 4 during the normal operation. The sample is accurately measured in the sample slot 25b and then is swept from such sample slot 25b upon a rotation of the sampler 25 to the position shown in FIG. 3A. The hydrogen and the sample thus pass through the pyrolysis tube P where any heavy hydrocarbons are broken down so that the carbon atoms form with the hydrogen to produce methane or other light hydrocarbon having a low molecular weight which is gaseous at ambient temperatures. The temperature in the pyrolysis tube P is approximately 700 centigrade, but the cabinet is relatively cool, normally being maintained in the neighborhood of approximately 70 F. by the heater K.

The gaseous sample and the excess hydrogen flow through the line 37 to the hydrogenator H where the sulfur and sulfur compounds in the sample are reacted with the hydrogen in the presence of the catalyst to produce hydrogen sulfide, the quantity of which is measured thereafter by the analyzer or measuring device C. Any excess sample is vented to the atmosphere through an outlet line 81.

Although the invention has been particularly described with respect to the analysis of sulfur and sulfur compounds in a liquid sample, the invention is applicable to the measurement of sulfur and sulfur compounds in a gaseous sample or in a solid sample. In a gaseous sample, the heavier hydrocarbons which may be gaseous because of being vaporized at relatively high temperatures are subject to the pyrolysis and are broken down into the lower molecular weight hydrocarbons so that the sample thereafter remains gaseous at ambient temperatures. Even if all of the entering sample is believed to be methane or a gas which is gaseous at ambient temperatures, some heavier hydrocarbons are usually present in the gas, and therefore, the pyrolysis is effective in breaking such heavier hydrocarbons down to methane so that all of the gas passed to the hydrogenation unit H for forming the hydrogen sulfide remains gaseous as it is processed.

If the sample is a solid, the sample itself must be first vaporized and this can be accomplished in the pyrolysis unit directly, thereby eliminating the flow control unit F, but the quantities of the sample must then be controlled by other means (not shown). Also, the solid can be vaporized by a separate pyrolysis unit and then in liquid or gaseous form introduced in the line 10 for flow and treatment in the same manner as heretofore described with respect to a liquid sample.

The hydrogen which is utilized in the method of this invention may be supplied in any suitable manner and it may be produced by a pyrolysis of the sample itself where the sample is a hydrocarbon. In some instances, the hydrogen may be produced in the same pyrolysis unit P as is used in the conversion of the hydrocarbon sample into the lighter hydrocarbon.

As previously explained, the system is periodically purged with nitrogen and the catalyst in the hydrogenator is activated, using the automatic catalyst reactivator R.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.

I claim:

1. A total sulfur analyzer for measuring the amount of sulfur present in various forms in a sample, comprismg:

means for converting the hydrocarbon sample into a lighter molecular weight hydrocarbon which is gaseous at ambient temperatures; and

hydrogenator means for reacting the lighter material with hydrogen to convert the sulfur in the material into hydrogen sulfide for subsequent measurement.

2. The structure set forth in claim 1, including:

means for measuring the quantity of hydrogen sulfide produced by the reaction with hydrogen in said lastmentioned means.

3. The structure set forth in claim 1, wherein:

said sample has at least one hydrocarbon which is not gaseous at ambient temperatures and said lighter molecular material is a hydrocarbon which is gaseous at ambient temperatures.

4. The structure set forth in claim 1, wherein said means for converting the sample is a pyrolysis unit.

5. The structure set forth in claim 1, including:

means for periodically reactivating the catalyst in said hydrogenator means automatically.

6. The structure set forth in claim 1, including:

means for receiving a continuous stream of said sample; and

flow control means for controlling the rate of flow of said sample to said converting means.

7. The structure set forth in claim 6, wherein said flow control means includes:

a rotary sampler having means therewith for receiving successive samples from the sample stream, each of which is of the same quantity; and

means for successively feeding each of said samples from said rotary sampler at equal time intervals to thereby control the sample flow rate through the analyzer.

8. The structure set forth in claim 7, wherein said means for successively feeding each of said samples includes:

means for forcing hydrogen gas through a portion of said sampler after each sample has been collected to sweep each sample into said converting means.

9. A method for measuring the total amount of sulfur present in a hydrocarbon sample, comprising the steps of:

converting the hydrocarbon sample into a lighter molecular weight hydrocarbon which is gaseous at ambient temperatures; and

reacting the lighter material with hydrogen to convert the sulfur in various forms in the sample into hydrogen sulfide for subsequent measurement.

10. The method set forth in claim 9, including:

measuring the quantity of hydrogen sulfide produced by the reaction of the lighter material with the hydrogen.

11. The method set forth in claim 9, including:

converting said sample by pyrolysis;

feeding said sample from a continuous stream and at a controlled flow rate to the point for said pyrolysis.

12. The method set forth in claim 11, including:

sweeping successive samples into an area for the pyrolysis, using hydrogen gas.

References Cited UNITED STATES PATENTS 9/1971 Stamm 23-230 R R. M. REESE, Assistant Examiner US. Cl. X.R. 

